This invention relates to the chemical control of tobacco suckers (i.e., axillary buds) via the application of certain 3-hydroxy and 3-alkanoyloxy-2-[1-(substituted-oxyimino)ethyl]-5-substituted-cyclohex-2-e n-1-one derivatives.
Tobacco crop management requires that the terminal growing meristem be removed so that the number of usable leaves and their quality can be optimized. The removal of the terminal meristem, a process called topping, encourages the rapid development of lateral buds. These lateral buds are known as suckers. These suckers, if allowed to grow, can interfere with the proper development of usable tobacco leaves resulting in serious economic losses for the grower.
Manual removal of these suckers is very labor intensive. Chemicals are used, therefore, to arrest the development of lateral buds after topping. These chemicals mimic the phenomenon of apical dominance in tobacco cultivation after the plants are topped and allow the optimal development of usable leaves. For details on this subject, please refer to pages 233-262 of Principles of Flue-cured Tobacco Production by S. N. Hawks, Jr. and W. K. Collins, North Carolina State University (1983), and pages 71-81 of Plant Growth Regulating Chemicals, Vol. I, Ed. L. G. Nickel, CRC Press (1983).
In the chemical control of tobacco suckers, it is important that the chemical operates systemically; i.e., it should inhibit sucker development even when applied to other parts of the tobacco plant. This is important because in field-grown tobacco, the axillary buds, or suckers, are hidden in large leaf whorls. Thus, it is very difficult to apply the chemical spray such that it will directly contact the axillary buds. However, if the chemical operates systemically, this problem can be avoided because the chemical can be effectively applied to the leaves of the tobacco plant or even as a soil drench.
The most commonly used chemicals for tobacco sucker control are maleic hydrazide and flumetrain. Maleic hydrazide is a systemic inhibitor and though effective, it is not without its problems. Treatment with maleic hydrazide tends to leave undesirably high levels of residues in the leaves.
U.S. Pat. No. 4,440,566, issued April 3, 1984, discloses compounds having the formula: ##STR1## wherein
R is most preferably alkyl of 1 to 3 carbon atoms, most preferably ethyl or propyl;
R.sup.1 is most preferably 3-trans-chloroallyl or 4-chlorobenzyl;
R.sup.2 and R.sup.3 are preferably each alkyl of 1 to 3 carbon atoms or one of R.sup.2 or R.sup.3 is hydrogen and the other is alkylthioalkyl having 2 through 8 carbon atoms, most preferably R.sup.2 and R.sup.3 are each methyl or one of R.sup.2 or R.sup.3 is hydrogen and the other is 2-ethylthiopropyl.
This patent teaches that these compounds exhibit herbicidal activity against grasses and are safe with respect to broadleaf crops and also may be employed to prevent or retard the growth of lateral buds in plants and to promote the thinning out of fruit in various fruit trees.
U.S. Pat. No. 4,624,696, issued November 25, 1986, discloses compounds having the formula: ##STR2## wherein R.sup.1 is alkyl of 1 to 4 carbon atoms, R.sup.2 is hydrogen or alkoxycarbonyl of 2 to 5 carbon atoms, R.sup.3 is a 5-membered heterocyclic structure which contains 1 to 3 heteroatoms from the group consisting of N, O, and S and may contain 1 or 2 double bonds and 1 or 2 substituents from the group consisting of C.sub.1 -C.sub.4 -alkyl, C.sub.1 -C.sub.4 -alkoxy, halogen, trifluoromethyl, C.sub.1 -C.sub.4 -alkoxymethyl, C.sub.1 -C.sub.4 -alkylthiomethyl, vinyl and phenyl, and R.sup.4 is a 5-membered to 7-membered heterocyclic structure which contains one heteroatom or ring member, or two identical or different heteroatoms or ring members, from the group consisting of N, O, S, SO, and SO.sub.2, may contain 1, 2, or 3 double bonds and is unsubstituted or substituted by not more than 2 alkyl or alkoxy groups, each of 1 to 4 carbon atoms, or is a radical of the Formula II ##STR3## where X and Y are each N, O, S, SO, or SO.sub.2, and salts of these compounds.
This patent teaches that R.sup.1 is preferably a radical having two or three carbon atoms. The patent describes the compounds as exhibiting herbicidal activity against grasses and safe with respect to a number of enumerated crops.
The patent also teaches that these compounds exhibit herbicidal activity against grasses and are safe with respect to a number of crops.
U.S. Pat. No. 4,596,877 discloses compounds having the formula ##STR4## wherein R.sup.1 is C.sub.1 -C.sub.4 alkyl and R.sup.2 is C.sub.3 -C.sub.5 chloroalkenyl. R.sup.1 is preferably ethyl or propyl.
The compounds are described as being effective to remove grasses while being safe for a number of crops.
U.S. Pat. No. 4,432,786 discloses compounds having the following formula and their salts: ##STR5## wherein
R.sup.1 is hydrogen or lower alkyl;
R.sup.2 and R.sup.3 are independently selected from the group consisting of hydrogen, lower alkyl, aryl having 6 through 10 carbon atoms (preferably phenyl), substituted aryl having 6 through 10 carbon atoms (preferably phenyl) and 1 through 4 substituents (preferably 1 or 2) independently selected from the group consisting of fluoro, chloro, bromo, iodo, or trifluoromethyl;
R.sup.4 is hydrogen or alkoxycarbonyl having 2 through 4 carbon atoms;
R.sup.5 is hydrogen, or an acyl group having 1 through 12 carbon atoms; and
Z is a group having the formula: ##STR6## wherein R.sup.6, R.sup.7, and R.sup.8 are independently selected from the group of hydrogen, halo, nitro, alkyl having 1 through 4 carbon atoms, alkoxy having 1 through 4 carbon atoms, or trifluoromethyl.
The compounds wherein R.sup.1 is ethyl or propyl and/or Z is a chlorothienyl are preferred. The compounds are described as exhibiting excellent grass herbicidal activity.
Certain 2-acyl-3-hydroxy-5-heterocyclecyclohexenone derivatives are described in German application DE No. 3,522,213 laid open January 2, 1987, as exhibiting a variety of plant growth regulating activities including preventing suckering in tobacco.
Commonly assigned U.S. application Ser. No. 854,448 filed Apr. 21, 1986, non U.S. Pat. No. 4,701,205 discloses that certain 2-[1-(3-chloroallyloxyimino)ethyl]-3-hydroxy-5-(2-substituted thioalkylidene)-cyclohex-2-en-1-one derivatives are useful to control tobacco suckers.